List Of Footnotes

1		The star claimed to be “the closest ever solar twin” (Porto de Mello and da Silva, 1997 ), HR 6060, shows parameters nearly indistinguishable from solar values indeed: $L∕L⊙$ = 1.05 $±$ 0.02; spectral type G2 Va (Sun: G2 V); B–V = 0.65 (Sun: 0.648); U–B = 0.17 (Sun: 0.178); T_eff = 5789 K (Sun: 5777 K; $Δ$ T_eff = 12 $±$ 30 K); log g = 4.49 (Sun: 4.44; $Δ$ log g = 0.05 $±$ 0.12), microturbulence velocity $ξ$ = 1.54 km s^–1 (Sun: 1.52 km s^–1; $Δ ξ$ = [0.02 $±$ 0.04] km s^–1); element abundances solar within 1 $σ$ , in particular [Fe/H] = 0.05 $±$ 0.06; Mount Wilson activity index $< S >$ = 0.174 (Sun: 0.177 in 1980); rotational velocity v sin i $<$ 3.0 km s^–1 (Sun: v = 2 km s^–1).
2		The line fluxes of O viii, O vii, N vii, and C vi were determined from a model spectrum synthesized in the XSPEC software (Arnaud, 1996 ) using the vapec model (Smith et al., 2001 ). The model is based on an isothermal plasma with a temperature of 2 MK normalized such that the 0.1–10 keV luminosity is 2 $×$ 10²⁷ erg s^–1. The low-FIP element abundances were set to values four times higher than standard photospheric abundances, while the high-FIP element abundances were photospheric; the S abundance was set to an intermediate value of 2 $×$ the photospheric value.
3		Meyer normalized the abundances such that the low-FIP element abundances were photospheric and the high-FIP abundances depleted, whereas the present-day view is that high-FIP elements are at photospheric levels, see Feldman (1992 ).